UMASS/AMHERST         • 


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LIBRARY 


OF  THE 


MASSACHUSETTS 

AGRICULTURAL 

COLLEGE 


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V.2 


MASSACHUSETTS  SOCIETY  FOR  PROMOTING 
AGRICULTURE. 


RESULTS  OF 
SPRAYING  EXPERIMENTS 

AGAINST 

CATERPILLARS  OF  THE  GYPSY 

AND  BROWN-TAIL 

MOTHS 


May,  1905 


See  last  page  of  the  cover 


MASSACHUSETTS  SOCIETY  FOR  PROMOTING 
AGRICULTURE. 


RESULTS  OF 
SPRAYING  EXPERIMENTS 

AGAINST 

CATERPILLARS  OF  THE  GYPSY 

AND  BROWN-TAIL 

MOTHS 


May,  190^ 


See  last  page  of  the  cover 


ARNOLD  ARBORETUM,  HARVARD  UNIVERSITY. 


Jamaica  Plain,  Mass.,  June  8,  1905. 

To  THE  Trustees  of  the  Massachusetts  Society  for 

Promoting  Agriculture  : 

Dear  Sirs : — Your  committee  appointed  to  consider 
methods  for  the  suppression  of  the  gypsy  and  browntail 
moths  in  Massachusetts  make  the  following  report: 

The  possibility  of  killing  these  moths  by  poisoning  the 
foliage  of  the  plants  on  which  they  feed  not  having,  it 
appeared,  been  fully  recognized  in  this  State,  your  Commit- 
tee arranged  in  May  for  a  public  exhibition  of  this  meth- 
od of  insect  destruction  on  a  scale  large  enouo-h  to  be  con- 
elusive. 

The  trial  was  made  on  May  22nd  and  continued  through 
four  days,  and  on  May  31st  and  June  1st  was  supple- 
mented by  an  additional  application  of  poison  to  prevent 
invasion  from  unsprayed  woods  and  trees  in  the  neighbor- 
hood. The  work  was  done  under  the  direction  of  Mr.  J. 
A.  Pettigrew,  Superintendent  of  the  Boston  Park  System, 
whose  report  on  the  details  of  the  work  with  its  cost  is 
appended. 

The  piece  of  land  in  Melrose  selected  for  the  experi- 
ment, 11. 4  acres  in  extent  (the  area  as  given  by  the  engi- 
neers of  the  Metropolitan  Park  Commission),  was  covered 
with  a  growth  of  White  Pines,  Oaks,  Beeches,  Apple- 
trees,  Willows  and  Hop  Hornbeams,  and  with  a  dense 
undergrowth  of  Alders,  Sumachs,  Barberries,  Witch 
Hazel  and  seedling  trees  of  several  species.  All  the  trees 
were  badly  infested  with  the  nests  of  the  browntail  moth 
and  the  egg-clusters  of  the  gypsy  moth,  and  old  walls  and 


piles  of  stone  gave  safe  and  convenient  shelter  for  egg- 
clusters.  No  work  of  suppression  of  any  sort  had  been 
attempted  on  this  land  which  appeared  to  your  Committee 
to  be  as  badly  infested  as  any  piece  of  land  of  similar  size 
that  could  be  found  in  the  state. 

The  difficulty  and  expense  of  thoroughly  poisoning  the 
foliage  on  this  particular  piece  of  land  was  increased  by 
the  thick  growth  of  trees  and  shrubs  and  by  the  unusual 
height  of  many  of  the  trees.  Several  Pines  and  Elms  ex- 
ceed a  height  of  seventy  to  eighty  feet,  and  could  be 
covered  with  poison  only  by  the  use  of  a  forty  to  sixty 
foot  ladder,  the  average  size  of  all  the  trees  being  proba- 
bly much  above  that  of  the  forest  growth  in  the  infested 
region.  Spraying  operations  were  simplified  by  the  fact 
that  every  part  of  the  land  could  be  reached  by  hose  from 
the  pump  stationed  on  a  highroad,  and  by  the  convenient 
access  to  water.  Setting  the  height  of  the  trees,  their 
number  and  the  dense  undergrowth  against  the  exception- 
able facilities  for  operating  the  pump  and  obtaining  a 
supply  of  water,  the  cost  of  the  first  four  days'  work 
(-121.87  per  acre),  exclusive  of  the  cost  of  the  machine 
and  hose,  can  perhaps  be  safely  taken  as  a  fair  average 
cost  per  acre  of  thoroughly  spraying  woods  in  any 
part  of  the  infested  region.  More  powerful  machinery, 
better  adapted  to  spraying  on  a  large  scale,  and  some  cheap- 
er form  of  poison  may,  however,  be  expected  to  reduce 
the  cost  of  the  operation. 

A  careful  inspection  of  the  sprayed  area  made  on  June 
7th  showed  that  the  foliage  had  not  been  destroyed.  Only 
a  few  half-dead  caterpillars,  too  feeble  to  be  dangerous  and 
soon  to  die,  could  be  found  on  the  leaves,  while  piles  of 
dead  caterpillars  on  the  ground  showed  the  effect  of  the 


poison.  Trees  in  the  neighborhood  that  had  not  been 
sprayed,  and  on  which  no  work  of  suppression  had  been 
done,  were  on  June  7th  entirely  denuded  of  leaves.  So 
far  therefore  as  killing  the  caterpillars  on  this  piece  of 
ground  is  concerned  the  experiment  has  been  entirely  suc- 
cessful.    It  shows: — 

First,  that  it  is  practicable  to  apply  poison  to  the  foli- 
age of  trees  crowded  in  woods  in  sufficient  quantities  to 
insure  the  death  of  all  insects  feeding  on  it ;  and  that  it  is 
not  necessary  to  try  other  means  of  destruction  if  the 
spraying  is  done  effectively  and  at  the  right  time. 

Second,  that  this  method  of  destruction  of  the  gypsy 
and  browntail  moths  is  cheaper  and  more  effective  than 
any  of  the  methods  which  have  been  in  general  use  for 
the  destruction  of  these  insects. 

Third,  that  this  method  makes  possible  the  preservation 
of  the  young  trees  and  shrubs  neccessary  for  the  perpetu- 
ation and  beauty  of  the  forest,  previous  attempts  to  de- 
stroy the  gypsy  moth  on  trees  growing  in  woods  being 
dependent  on  the  destruction  of  all  small  plants  able  to 
afford  them  shelter  and  retreat. 

Of  the  possibility  of  the  easy  destruction  of  the  caterpil- 
lars of  the  browntail  moth  by  arsenical  poison  when  they  are 
fully  grown  in  spring  or  in  September  when  they  are  first 
hatched  there  is  no  question.  Our  experiment  has  shown 
that  it  is  practicable  to  kill  by  arsenical  poison  the  caterpil- 
ars  of  the  gypsy  moth  when  they  are  first  hatched,  but  it  is 
still  to  be  demonstrated  that  poisoning  is  effective  against 
the  full  grown  caterpillar,  and  it  is  evident  that  the  mature 
caterpillars  entering  a  sprayed  territory  will  not  be  killed 
by  poison  applied  six  weeks  earlier  to  trees  which  have 
produced    new    leaves  since  the    application    was  made. 

5 


Spraying,  to  be  really  effective,  must  be  general,  or,  if  it 
is  not  general,  sprayed  ground  must  be  protected  from  in- 
vasion by  some  mechanical  device. 

Of  the  value  of  spraying  against  these  insects  on  iso- 
lated street  or  orchard  trees  there  can  be  no  question. 
For  such  trees  no  matter  what  their  size  may  be,  it  is  ef- 
fective and  cheap.  A  comparison  now  of  some  of  the 
large  Elm  trees  on  the  sprayed  territory  on  Wyoming 
Avenue  with  the  Elm  trees  of  similar  size  on  many  streets 
of  the  infested  district  will  show  the  value  of  arsenical 
poison.  In  many  cases  these  street  trees  have  been  care- 
fully and  laboriously  cleared  of  egg-clusters  and  nests,  but 
the  impossibility  of  getting  the  last  cluster  or  the  last  nest 
is  shown  by  the  presence  on  these  trees  of  enough  cater- 
pillars to  defoliate  them.  The  impossibility  of  destroying 
all  the  egg-clusters  of  the  gypsy  moth  in  any  given  locality 
is  well  shown,  too,  at  this  time  in  the  Middlesex  Fells 
where  thousands  of  the  caterpillars  can  be  seen  on  trees 
in  regions  from  which  all  undergrowth  has  been  removed 
and  where  it  was  believed  every  egg-cluster  had  been 
killed. 

C.  S.  Sargent,  i 

John  Lowell,  V  Committee. 

H.  S.  HUNNEWELL,    ) 


Boston,  June  6,  1905. 

Professor  Charles  S.  Sargent,  President, 

Mass.  Society  for   Promoting  Agriculture, 
Dear  Sir: 

Agreeably  to  your  request  that  I  take  charge  of  an  ex- 
periment proposed  by  your  Society  for  the  suppression  of 
the  gypsy  and  brown-tail  moths,  by  spraying  the  foliage 

6 


attacked  by  them  with  an  arsenical  solution,  I  arranged  for 
the  mounting  of  a  Worthington  steam  pump,  of  35  gallons 
per  minute  capacity,  on  the  frame  of  a  portable  steam  boil- 
er of  8  horse  power,  the  whole  costing  !$485.00  which  at- 
tached to  an  ordinary  600igallon  street  sprinkler,  made  an 
apparatus  capable,  under  a  pressure  of  120  lbs.  per  square 
inch  in  the  pump  chambers  of  projecting  two  streams  from 
•  3/16  inch  diameter  nozzles  to  a  height  of  fifty  to  sixty  feet. 
Another  stream  conducted  through  a  perforated  pipe  into 
the  sprinkling  tub  served  as  an  agitator  for  the  poisonous 
solution  used.  200  feet  of  1  1/2  inch  diameter  hose  was 
used  as  a  main  supply  for  the  two  distributing  hose,  which 
were  each  200  feet  in  length,  the  first  100  feet  being  of  one 
inch  diameter  while  the  second  100  feet  of  each  was  3/4  of 
an  inch  in  diameter,  on  the  ends  of  which  were  the  nozzles. 
An  additional  street  sprinkler  of  600  gallons  capacity 
was  used  as  an  alternate  to  keep  the  pump  in  constant  use. 
A  single  horse  supply  wagon,  three  sets  of  40-foot  exten- 
sion ladders,  and  a  corps  of  eight  men,  one  foremen,  two 
teamsters,  and  an  engineer  completed  the  equipment. 

The  piece  of  woodland  selected  by  you  was  located  at 
the  junction  of  Ravine  Road  and  Wyoming  Avenue,  adjoin- 
ing the  Middlesex  Fells  Reservation,  being  entirely  bound- 
ed by  these  roads  and  containing  11.4  acres.  It  is  filled 
with  a  heavy  and  tall  growth  of  pines  and  deciduous  trees, 
which  were  badly  infested  with  gypsy  and  brown-tail 
moths. 

When  the  work  of  spraying  commenced,  on  May  22, 
the  gypsy  larvae  were  about  3/8  of  an  inch  long,  and 
the  brown  tail  larvae  about  5/8  to  1  inch  long.  The 
spraying  was  completed  in  four  days.  Subsequently,  a 
lighter  gasoline  machine  of  three  and  one-half  horse  power, 


and  four  men  were  employed  for  4  days  from  May  31  in 
adding  a  second  coat  of  the  solution,  at  the  edge  of  the 
woodland  to  a  depth  of  fifty  or  seventy-five  feet,  to  meet 
the  present  invasion  of  brown-tail  larvae  from  the  woods 
across  the  boundery  roads,  and  of  the  gypsy  larvae  later. 

Disparene,  a  composition  of  arsenate  of  soda  and  ace- 
tate of  lead,  was  used  in  the  proportion  of  ten  pounds  of 
the  solution  to  one  hundred  gallons  of  water.  At  least 
two-thirds  of  the  area  had  to  be  sprayed  from  ladders,  on 
account  of  the  height  of  the  trees  about  160  of  them  being 
60  feet  high  and  upwards.  When  conditions  were  favor- 
able, foliage  seventy-five  feet  distant  laterally  could  be  cov- 
ered with  fine  spray.  To  make  the  solution  more  adhesive  to 
the  foliage,  flour,  molasses,  and  glucose  were  each  tried  in 
turn,  being  mixed  with  the  solution :  the  result  in  each 
case  was  satisfactory. 

The  net  cost  of  first  spraying  was  $249.09,  or  at 
the  rate  of  $21.87  per  acre.  With  the  supplemental 
spraying  of  the  borders  included,  the  net  cost  was  1338.04, 
or  1)29.65  per  acre.  The  total  cost  of  the  work  was  $394.34. 
This  includes  cost  of  transport  of  equipment  to  and  fro, 
and  for  time  lost  by  men  working  so  far  from  home,  which 
is  deducted  as  not  being  a  legitimate  charge  in  the  cost  of 
the  work. 

The  poison  was  found  to  be  effective  against  the  gypsy 
larvae  on  the  second  day,  many  being  dead,  others  appear- 
ing sick  and'^ torpid.  In  a  week  the  effect  was  much  more 
noticeable,  the  larger  and  stronger  brown-tail  larvae  being 
also  similarly  affected,  while  nearly  all  of  the  larvae  of  the 
gypsy  moth  were  dead. 

Very  Respectfully  submitted, 

J.  W.  Pettigrew. 


BROWN-TAIL  MOTHS. 

March  18th.  The  caterpillars  begin  to  leave  nests,  and 
commence  eating. 

June  10th.     Commence  to  spin  cocoons  and  pupate. 

July  1st.  The  white  moths,  with  a  brown  tail,  commence 
to  emerge  from  the  pupal  stage,  and  soon  begin  to  lay 
eggs.     The  eggs  hatch  in  from  15  to  20  days. 

July  20th.  They  begin  to  feed  about  this  time,  and  feed 
for  about  six  weeks. 

Sept.  1st.     The)'  liegin  to  form  their  winter  nests. 


GYPSY  MOTHS. 

April  30th.     Egg-clusters  commence  to   hatch,  and  cater- 
pillars begin  to  feed  about  this  time. 

July  15th.      They  commence  to  pupate  about  this  time. 

July  25th.     The  moths  commence  to   appear,  and   soon 
commence  laying  egg-clusters. 


